The long term goal of the animal research is to develop new techniques for treating some forms of congenital heart disease through the use of percutaneous transluminal angioplasty procedures. More specifically, the work is designed to evaluate catheter balloon dilatation to treat aortic valve stenosis, create localized septal defects, and dilate stenotic systemic-pulmonary shunts. The experimental procedures to be evaluated may have direct clinical application by providing new non-surgical approaches to treating infants and young adults suffering from congenital heart conditions. Dogs will be used for the studies. The hemodynamic effects of balloon occlusion of the aortic outflow tract will be evaluated in animals with aortic banding induced left ventricular hypertrophy. The ability of the aortic annulus to tolerate varying degrees of overdistension produced by large diameter balloon angioplastic catheters will also be evaluated. Fixed diameter catheter balloon dilatation of the interatrial wall will also be studied in dogs. The risks and effectiveness of the fixed balloon atrial septal defect dilatation procedure will be compared to current pull-through and/or blade septostomy procedures. Finally, dogs with surgically native and Gortex systemic-pulmonary shunts will be studied to evaluate morphological results of angioplasty dilatation and overdilatation of the shunts. Clinical experience indicates that stenotic pulmonary-systemic shunts do not respond to angioplasty procedures as successfully as similar stenotic shunts in the iliac and femoral region. Results of the studies should provide important data relating to the potential clinical application of non-surgical, percutaneous transcatheter balloon dilatation procedures for treating congenital heart disease. The studies should also extend our current knowledge regarding the limitations and potential risk:benefit ratio of such procedures.